.\" RCSid "$Id: pdfblur.1,v 1.7 2008/11/10 19:08:17 greg Exp $"

.TH PDFBLUR 1 1/24/96 RADIANCE

.SH NAME

pdfblur - generate views for depth-of-field blurring

.SH SYNOPSIS

.B pdfblur

.B aperture

.B nsamp

.B viewfile

.SH DESCRIPTION

.I Pdfblur

takes the given

.I viewfile

and computes

.I nsamp

views based on an aperture diameter of

.I aperture

(in world coordinate units) and a focal distance equal to the length of the

.I \-vd

view direction vector.

When rendered and averaged together, these views will result in

a picture with the specified depth of field.

Either

.I pinterp(1)

or

.I rpict(1)

may be called to do the actual work.

(The given

.I viewfile

must also be passed on the command line to the chosen renderer, since

.I pdfblur

provides supplemental view specifications only.)\0

.PP

For

.I pinterp,

feed the output of

.I pdfblur

to the standard input of

.I pinterp

and apply the

.I \-B

option to blur views together.

In most cases, a single picture with z-buffer is all that is required

to get a satisfactory result, though the perfectionist may wish to

apply three pictures arranged in a triangle about the aperature, or

alternatively apply the

.I \-ff

option together with the

.I \-fr

option of

.I pinterp.

(The latter may actually work out to be faster, since rendering

three views takes three times as long as a single view, and the

.I \-fr

option will end up recomputing relatively few pixels by

comparison.)\0

.PP

To use

.I pdfblur

with

.I rpict,

apply the

.I \-S

option to indicate a rendering sequence, and set the

.I \-o

option with a formatted file name to save multiple output

pictures.

When all the renderings are finished, combine them with the

.I pcomb(1)

program, using appropriate scalefactors to achieve an average.

Note that using

.I rpict

is MUCH more expensive than using

.I pinterp,

and it is only recommended if the scene and application

absolutely demand it (e.g. there is prominent refraction that

must be modeled accurately).

.PP

For both

.I pinterp

and

.I rpict,

the computation time will be proportional to the number of views from

.I pdfblur.

We have found a

.I nsamp

setting somewhere between 5 and 10 to be adequate for most images.

Relatively larger values are appropriate for larger aperatures.

.PP

The

.I \-pd

option of

.I rpict

may be used instead or in combination with or instead of

.I pdfblur

to blur depth-of-field.

If used in combination,

it is best to set the

.I \-pd

option to the overall

.I aperture

divided by

.I nsamp

to minimize ghosting in the output.

.PP

To simulate a particular camera's aperture, divide the focal length of

the lens by the f-number, then convert to the corresponding

world coordinate units.

For example, if you wish to simulate a 50mm lens at f/2.0 in

a scene modeled in meters, then you divide 50mm by 2.0 to get 25mm,

which corresponds to an effective aperture of 0.025 meters.

.SH EXAMPLES

To use

.I pinterp

to simulate an aperture of 0.5 inches on a lens focused at a

distance of 57 inches:

.IP "" .2i

rpict \-vf myview \-x 640 \-y 480 \-z orig.zbf scene.oct > orig.hdr

.br

pdfblur 0.5 57 8 orig.hdr | pinterp \-B \-vf orig.hdr \-x 640 \-y 480

orig.hdr orig.zbf > blurry.hdr

.PP

To use

.I rpict

exclusively to do the same:

.IP "" .2i

pdfblur .5 57 5 myview | rpict \-S 1 \-vf myview \-x 640 \-y 480

\-o view%d.hdr scene.oct

.br

pcomb \-s .2 view1.hdr \-s .2 view2.hdr \-s .2 view3.hdr \-s .2

view4.hdr \-s .2 view5.hdr > blurry.hdr

.SH AUTHOR

Greg Ward

.SH BUGS

This program really only works with perspective views.

.SH "SEE ALSO"

pcomb(1), pinterp(1), pmblur(1), pmdblur(1), rcalc(1), rpict(1), vwright(1)